Fix thread safe issue

Declare ReaderIndex[] as _Atomic as it can be accessed from 2 different
threads.

==================
WARNING: ThreadSanitizer: data race (pid=4017)
  Write of size 4 at 0x7fd1b32be970 by main thread (mutexes: write M0, write M1):
    #0 ReleaseReaderIndex CCID/src/utils.c:81:21 (libccid.so+0xa672) (BuildId: 69b3a74d7af87f05c5edb71935a43b024a0fe968)
    #1 FreeChannel CCID/src/ifdhandler.c:92:2 (libccid.so+0xa672)
    #2 IFDHCloseChannel CCID/src/ifdhandler.c:302:2 (libccid.so+0xa672)
    #3 IFDCloseIFD PCSC/src/ifdwrapper.c:190:7 (pcscd+0xd9e30) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #4 RFUnInitializeReader PCSC/src/readerfactory.c:1153:9 (pcscd+0xd9e30)
    #5 removeReader PCSC/src/readerfactory.c:645:2 (pcscd+0xd9e30)
    #6 _UnrefReader PCSC/src/readerfactory.c:120:3 (pcscd+0xd9e30)
    #7 IFDCloseIFD PCSC/src/ifdwrapper.c:190:7 (pcscd+0xd9e30) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #8 RFUnInitializeReader PCSC/src/readerfactory.c:1153:9 (pcscd+0xd9e30)
    #9 removeReader PCSC/src/readerfactory.c:645:2 (pcscd+0xd9e30)
    #10 _UnrefReader PCSC/src/readerfactory.c:120:3 (pcscd+0xd9e30)
    #11 RFRemoveReader PCSC/src/readerfactory.c:624:5 (pcscd+0xdd282) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #12 RFRemoveReader PCSC/src/readerfactory.c:624:5 (pcscd+0xdd282) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #13 RFRemoveReader PCSC/src/readerfactory.c:624:5 (pcscd+0xdd282) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #14 RFCleanupReaders PCSC/src/readerfactory.c:1396:9 (pcscd+0xddb9e) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #15 SVCServiceRunLoop PCSC/src/pcscdaemon.c:123:4 (pcscd+0xd9574) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #16 main PCSC/src/pcscdaemon.c:801:2 (pcscd+0xd8810) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)

  Previous read of size 4 at 0x7fd1b32be970 by thread T7:
    #0 LunToReaderIndex CCID/src/utils.c:72:14 (libccid.so+0xf8aa) (BuildId: 69b3a74d7af87f05c5edb71935a43b024a0fe968)
    #1 IFDHPolling CCID/src/ifdhandler.c:313:28 (libccid.so+0xb1bf) (BuildId: 69b3a74d7af87f05c5edb71935a43b024a0fe968)
    #2 EHStatusHandlerThread PCSC/src/eventhandler.c:467:10 (pcscd+0xd6f9b) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)

  As if synchronized via sleep:
    #0 nanosleep <null> (pcscd+0x515ed) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #1 SYS_Sleep PCSC/src/sys_unix.c:69:9 (pcscd+0xdfbf9) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #2 SVCServiceRunLoop PCSC/src/pcscdaemon.c:117:10 (pcscd+0xd956a) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #3 main PCSC/src/pcscdaemon.c:801:2 (pcscd+0xd8810) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)

  Location is global 'ReaderIndex' of size 64 at 0x7fd1b32be970 (libccid.so+0x22970)

  Mutex M0 (0x7b0c00000ed0) created at:
    #0 pthread_mutex_init <null> (pcscd+0x555cf) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #1 RFAddReader PCSC/src/readerfactory.c:355:9 (pcscd+0xdb4b7) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #2 HPAddDevice PCSC/src/hotplug_libudev.c:512:8 (pcscd+0xe3409) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #3 HPScanUSB PCSC/src/hotplug_libudev.c:579:3 (pcscd+0xe2a1d) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #4 HPRegisterForHotplugEvents PCSC/src/hotplug_libudev.c:761:2 (pcscd+0xe2a1d)
    #5 main PCSC/src/pcscdaemon.c:768:7 (pcscd+0xd8717) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)

  Mutex M1 (0x7fd1b32be948) created at:
    #0 pthread_mutex_lock <null> (pcscd+0x71ada) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #1 CreateChannelByNameOrChannel CCID/src/ifdhandler.c:119:8 (libccid.so+0x82ae) (BuildId: 69b3a74d7af87f05c5edb71935a43b024a0fe968)
    #2 IFDHCreateChannelByName CCID/src/ifdhandler.c:233:9 (libccid.so+0x7e55) (BuildId: 69b3a74d7af87f05c5edb71935a43b024a0fe968)
    #3 IFDOpenIFD PCSC/src/ifdwrapper.c:136:9 (pcscd+0xdd0cb) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #4 RFInitializeReader PCSC/src/readerfactory.c:1121:8 (pcscd+0xdd0cb)
    #5 RFAddReader PCSC/src/readerfactory.c:366:7 (pcscd+0xdb52a) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #6 RFAddReader PCSC/src/readerfactory.c:366:7 (pcscd+0xdb52a) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #7 HPAddDevice PCSC/src/hotplug_libudev.c:512:8 (pcscd+0xe3409) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #8 HPScanUSB PCSC/src/hotplug_libudev.c:579:3 (pcscd+0xe2a1d) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #9 HPRegisterForHotplugEvents PCSC/src/hotplug_libudev.c:761:2 (pcscd+0xe2a1d)
    #10 main PCSC/src/pcscdaemon.c:768:7 (pcscd+0xd8717) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)

  Thread T7 (tid=4049, running) created by thread T4 at:
    #0 pthread_create <null> (pcscd+0x53dfd) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #1 ThreadCreate PCSC/src/utils.c:184:8 (pcscd+0xe3cab) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #2 EHSpawnEventHandler PCSC/src/eventhandler.c:233:7 (pcscd+0xd6840) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #3 RFAddReader PCSC/src/readerfactory.c:397:8 (pcscd+0xdb6ba) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #4 HPAddDevice PCSC/src/hotplug_libudev.c:512:8 (pcscd+0xe3409) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)
    #5 HPEstablishUSBNotifications PCSC/src/hotplug_libudev.c:646:6 (pcscd+0xe3783) (BuildId: 046d0874ce19c882d4f3b8ab5213aa4cd336cd5e)

SUMMARY: ThreadSanitizer: data race CCID/src/utils.c:81:21 in ReleaseReaderIndex
==================

src/utils.c

@@ -27,7 +27,7 @@
 #include "utils.h"
 #include "debug.h"
 
-int ReaderIndex[CCID_DRIVER_MAX_READERS];
+_Atomic int ReaderIndex[CCID_DRIVER_MAX_READERS];
 #define FREE_ENTRY -42
 
 void InitReaderIndex(void)